Coating process

ABSTRACT

In the process described, cyclic polyimino ethers with Δ 2  -oxazoline or Δ 2  -5,6-dihydro-4H-1,3-oxazine structure are applied, alone or together with cyclic monoimino ethers of the same type, or with lactones, plus cationic polymerization catalysts, to solid surfaces and polymerized by heating. The process gives smooth, glossy coatings with high adhesive strength, hardness, and elasticity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to surface coating and, more particularly, to the low-solvent coating of solid surfaces.

2. Statement of Related Art

Solvent-containing lacquers and paints are mainly used in conventional processes for coating solid surfaces, especially metal and wood surfaces. In an effort to save organic solvents or to avoid them for ecological or safety reasons, water-based lacquers on the one hand and low-solvent and solventless coating systems on the other hand have recently been developed in addition to conventional lacquers and paints. In the field of low-solvent and solventless coating systems, a distinction is drawn between so-called powder lacquers and coatings applied in a liquid form. In powder lacquer technology, curable compounds or preformed thermoplastic polymers are applied to the surface in finely divided form, generally by electrostatic spraying, and are generally cured or melted to form a film by exposure to heat. The systems applied in liquid form are generally reactive compounds of relatively low molecular weight which polymerize on the surface and thus form a solid film.

For coating systems of this type applied in liquid form, only a few of the large number of polymerizable compounds have so far been successful. Polymerizable cyclic iminoethers have not hitherto been proposed as compounds for coating systems of this type. Solventless and low-solvent lacquers based on reactive epoxides, isocyanates, acrylates and melamine resins, some of which give very high-quality coatings, are of importance today. However, they are only used in narrow fields of application because not least their price and certain toxicological objections to some of the reactive components are obstacles to their use on a wide scale. A further explanation of the prior art can be found in the specialist literature, cf. for example Ullmanns Encyklopadie der technischen Chemie, 4th Edition, Vol. 15, Weinheim (1978), pages 590 et seq. and the original literture cited therein.

DESCRIPTION OF THE INVENTION Summary of the Invention

For the reasons explained above, there is still a need to develop new and altogether more advantageous coating processes. The present invention addresses this problem.

The present invention relates to a process for coating solid surfaces in which a mixture of

a) a cyclic polyiminoether having a Δ² -oxazoline or Δ² -5,6-dihydro-4H-1,3-oxazine structure,

b) optionally at least one compound from the group of cyclic monoiminoethers having a Δ² -oxazoline or Δ² -5,6-dihydro-4H-1,3-oxazine structure or from the group of lactones containing 4, 5, 6 or 7 ring members,

c) a cationic polymerization catalyst and

d) optionally auxiliaries and additives typically encountered in coatings

is applied to the surfaces and is polymerized on the surface by heating.

The process according to the invention is suitable for surfaces of various materials, including metal, wood, glass and plastics, providing they are capable of withstanding the temperatures required for curing. It leads to compact, smooth coatings which are distinguished by high adhesive strength, hardness and elasticity and by high gloss. Another advantage over known systems is that the final polymerizable mixture can be stored for very long periods at room temperature.

DESCRIPTION OF PREFERRED EMBODIMENTS

The individual components of the mixture to be applied to the surface are described in more detail in the following. Where reference is made to earlier publications, their respective disclosures are specifically included in the subject matter of the present application.

Component a

Suitable cyclic polyminoethers are compounds which contain the group ##STR1## two or more times in their molecule. In formula I, Z is either a direct bond or the group CR⁵ R⁶ and the substituents R¹ to R⁶ independently of one another represent H, alkyl or aryl containing up to 8 carbon atoms. Polyiminoethers in which at least 4 of the substituents R¹ to R⁶ are hydrogen atoms and the others consist of C₁₋₃ alkyl are preferred. Compounds in which I is a 2-Δ² -oxazoline group, i.e. Z is a direct bond, are also preferred. Of these compounds, those having the following substitution patterns are particularly preferred:

R¹ =CH₃, R² -R⁴ =H

R³ =CH₃, C₂ H₅ or phenyl; R¹, R² and R⁴ =H

Polyiminoethers in which all the substituents R¹ to R⁶ are hydrogen atoms are most particularly preferred.

The cyclic polyiminoethers used preferably contain the group I two, three or four times and are also referred to as bis-, tris- and tetrakis-oxazolines or bis-, tris- and tetrakis-(5,6-dihydro-4H-1,3-oxazines). Bisiminoethers are particularly preferred.

Cyclic polyiminoethers suitable for the purposes of the invention are known per se. They are normally prepared from di- or polycarboxylic acids or derivatives thereof and correspondingly substituted alkanolamines or equivalent reactants by cyclizing condensation similarly to the preparation of cyclic monoiminoethers from monocarboxylic acids and derivatives thereof. Examples of suitable polyiminoethers and their preparation can be found in DE 2 029 524, DE-OS 2 158 615, DE-OS 3 047 759 and EP-A 273 368. Typical representatives are tetramethylene bisoxazoline; p-phenylene bisoxazoline and 1,4-cyclohexylene bis-(5,6-dihydro-4H-1,3-oxazine).

Another method of preparing cyclic polyiminoethers starts out from cyclic monoiminoethers which contain the group I only once and which bear a reactive group at the substituent in the 2 position. Monoiminoethers such as these are also known per se and can be obtained by conventional methods, generally from monocarboxylic acids or derivatives thereof (see, for example, A. Levy and M. Litt, J. Polym. Sci. A1, 6 1883 (1968); S. Kobayashi and T. Saegusa in Ring-Opening Polymerization, Vol. 2, Ed. K. J. Irvin, T. Saegusa, London 1984, page 761; and also EP 88118090.5 and EP 90107481.5). These monoiminoethers are attached to polyfunctional reagents by the reactive group, the polyiminoethers (a) suitable for the purposes of the invention being formed with the iminoether group (I) intact. Thus, 2-alkenyl oxazolines or 2-alkenyl oxazines may be attached to polymercaptans, for example in accordance with U.S. Pat. No. 4,593,103, or hydroxyl-functional oxazolines or oxazines may be attached to polyisocyanates to form polyiminoethers in accordance with PCT/EP90/00733. Di- and poly-iminoethers according to PCT/EP90/00733 are particularly preferred for the process according to the invention; they may still contain small quantities of free or masked polyisocyanate, depending on the process used for their production. In principle, these polyiminoethers could also be formed during the coating process from hydroxyl-functional monoiminoethers and the necessary quantities of polyisocyanate, although this would involve handling of the toxicologically unsafe polyisocyanates which can avoided in the manner described above.

Component b

In addition to the polyiminoethers (a), the mixtures used in accordance with the invention may contain compounds from the group of cyclic monoiminoethers, from the group of lactones or mixtures of both. Suitable monoiminoethers are Δ² -oxazolines and Δ² -oxazines substituted in the 2-position which, more precisely, are also referred to as 5,6-dihydro-4H-1,3-oxazines. They correspond to formula II: ##STR2## in which Z is a direct bond or represents the group CR⁵ R⁶ and R¹ to R⁶ are as defined for formula I; in the polyiminoethers (a) and the monoiminoethers (b), Z and R¹ to R⁶ may of course be independently selected within the scope of the definition. R is a C₁₋₂₁ and preferably C₆₋₁₇ aliphatic, aromatic or araliphatic radical attached via carbon which may optionally contain ether groups and may bear further substituents which do not affect the polymerization reaction.

Monoiminoethers in which at least four of the substituents R¹ to R⁶ are hydrogen atoms and the others consist of C₁₋₃ alkyl are preferred. The compounds in which Z is a direct bond are also preferred. Of these compounds, those having the following substitution patterns are particularly preferred:

R¹ =CH₃, R² -R⁴ =H

R³ =CH₃, CH₂ H₅ or phenyl; R¹, R² and R⁴ =H

Monoiminoethers in which all the substituents R¹ to R⁶ are hydrogen are most particularly preferred. The monoiminoethers of formula II suitable for the purposes of the invention are known per se and may be obtained by standard methods, mainly from monocarboxylic acids or derivatives thereof and corresponding alkanolamines or equivalent compounds by cyclizing condensation. Relevant particulars can be found in the literature cited under a) for monoiminoethers.

In addition to aromatically substituted iminoethers, such as 2-phenyl oxazoline, particular preference is attributed above all to the iminoethers obtainable from fatty acids in which R is a long-chain aliphatic radical containing 7 to 17 carbon atoms.

In addition to monoiminoethers, lactones having a 4-membered, 5-membered, 6-membered or 7-membered ring are suitable as component b. The unsubstituted compounds butyrolactone, valerolactone and caprolactone are particularly preferred, although these lactones may also be substituted, preferably by C₁₋₃ alkyl groups.

Ratio of a to b

The molar ratio of components a and b and the valency of component a largely determine the curing rate in the polymerization reaction and also the mechanical properties of the coating produced. Accordingly, components a and b are preferably in an equivalent ratio of 95:5 to 5:95 and, more particularly, 80:20 to 20:80, the equivalent weight being understood here to be the molecular weight divided by the number of iminoether groups present in the molecule (valency).

Component c

Suitable catalysts for the polymerization of components a and b are, generally, any catalysts which are capable of initiating a cationic polymerization and which are also known for the polymerization of cyclic iminoethers, for example from DE 12 06 585. The catalysts in question are generally Lewis acids or Bronsted acids or alkylating agents which are capable of forming salt-like compounds with the iminoethers and also the salt-like compounds themselves. Examples are trifluoromethanesulfonic acid methyl ester, o- and p-toluenesulfonic acid and N-methyl-2-phenyl oxazolinium trifluoromethanesulfonate. Since the cationic polymerization of cyclic iminoethers is a so-called living polymerization which, in principle, can always be continued at the chain ends by addition of other monomers, "living" polymers which may be prepared from component b alone are also suitable as catalysts for the process according to the invention.

Liquid catalysts and catalysts which readily dissolve in the mixture of a and b at room temperature are preferred for the purposes of the present invention. In selecting the catalysts, it is important to ensure that they are compatible with the coating substrate during and after polymerization.

The quantity of catalyst critically determines the polymerization rate, so that the curing conditions for the mixture as a whole (time, temperature) can largely be determined in advance through the choice of the quantity used. A quantity of 5×10⁻² to 10⁻⁵ moles of catalyst per equivalent of components a+b is normally sufficient. Quantities above or below these limits may of course also be used.

Component d

According to the invention, coatings of excellent quality can be obtained from components a and c alone or from components a, b and c alone, individual properties of the coatings, particularly their elasticity, also being variable within wide limits through the choice of the individual components and the quantities in which they are used. In addition, the properties of the mixture to be processed and of the final coating can also be varied by incorporation of further additives. In principle, suitable further additives are any of the auxiliaries and fillers typically used for conventional paints and lacquers, including for example dyes, pigments, thickeners, light stabilizers, solvents, plasticizers, resins and other binders.

The properties of the coatings can be adapted even more closely to the requirements of the substrate and the particular protective function intended through the use of resins and other binders of the type typically used in lacquer technology. Examples of such resins and binders are polyacrylate, polyester, chlorinated rubber, alkyd resin, polyurethane and polymeric iminoether (linear polymer of monoiminoethers corresponding to formula II). The quantity of resins and binders added is determined by the desired effect and may be freely selected within wide limits.

Thickeners and solvents are primarily used to adjust the rheological properties of the mixture to be used where it is liquid. Suitable organic solvents are, above all, aromatic hydrocarbons and chlorinated hydrocarbons. Solvents which evaporate below the curing temperature are preferred. Their percentage content in the mixture as a whole is normally not more than 50% by weight and is preferably between 1 and 20% by weight, although the total absence of organic solvents is particularly preferred. Suitable thickeners are both low molecular weight substances, such as for example modified hydrogenated fats, and also polymeric compounds, for example polyesters.

The color and transparency of the coatings can be varied as required by the addition of dyes, pigments and fillers. Whereas the polymers of a or a and b alone give transparent and substantially colorless surface coatings, lacquers of high covering power or transparent varnishes can be obtained with additions such as these. The quantity in which they are used is again determined by the desired effect.

In choosing the auxiliaries and additives, it is of course important to ensure that they do not affect the polymerization of components a and b. For example, substances having a base-like effect will generally not be used.

The quantity of auxiliaries and additives in the mixture to be polymerized may be extremely high without affecting the advantages of the process according to the invention. However, the total content of component d is not more than 70% by weight and, in particular, is not more than 50% by weight, based on the total mixture of components a, b, c and d. The lower limit is determined by the desired effect and, for example in the case of dyes, may be at 0.001% by weight or lower.

To carry out the process according to the invention, an intimate mixture is initially prepared from components a and c, and, optionally, b and/or d. The components may be added in any order. In general, the mixture remains stable for several days to several weeks at room temperature, so that the components do not have to be mixed immediately before use. This is of advantage above all when several small-scale coating processes have to be carried out discontinuously. However, it is of course also possible to mix all the components or individual components, particularly the catalyst c, only shortly before use. The late addition of the catalyst can be of advantage if the virtually indefinite storability of the mixture of a, b and optionally d is to be utilized. Finally, mixing of the components on the surface to be coated, which also leads to the process according to the invention, may be regarded as the extreme case.

If curing of the same components is not carried out on a surface to be coated, resins are obtained in many cases and may be used with advantage for other applications, for example as raw materials, adhesives or support materials. However, this is not the subject of the present invention.

Mixtures which are liquid at room temperature or at slightly elevated temperature, so that they may be applied to the surface by any of the techniques normally used for liquid lacquers, for example by spread coating, spray coating or dip coating, are preferably used in accordance with the invention. However, it is also possible to apply mixtures of solid components to the surface by any of the methods typically used in powder lacquer technology, for example by electrostatic spraying. In either case, application of components a to d to the surfaces is followed by a heat treatment because curing of the mixture at room temperature generally takes too long for practical application. The necessary temperatures and curing times may be varied within wide limits, above all through the quantity of component c, but are also determined by the reactivity and concentration of components a and b. Temperatures in the range from about 80° to about 250° C. and polymerization times in the range from about 5 to about 120 minutes may be taken as guides. The choice of the temperature and therewith the time is of course also governed by the sensitivity of the substrate and the other constituents of the coating. It may be advisable in some cases to carry out the heat treatment in an inert gas atmosphere. The mixture may be heated by various methods, for example with warm air, by radiation, such as infrared or microwave radiation, or by contact heating of the surface to be coated from the rear. In practice, therefore, the choice of a suitable heating process can be entirely determined by external parameters of the process, for example by whether the process is carried out continuously or discontinuously.

EXAMPLES

In the following Examples, mixtures of components a and c and optionally b and d were prepared and applied by coating knife to plates of various materials. After heat treatment in a recirculating air drying cabinet, the properties of the films obtained are tested by the methods typically used in paint technology.

The following starting materials were used:

Component a

The polyiminoethers a1 to a9 used were prepared from equivalent quantities of commercially available polyisocyanates and hydroxyl-functional monoiminoethers in accordance with earlier patent application PCT/EP90/00733. The monoiminoethers in turn had been prepared from hydroxycarboxylic acids or esters thereof and ethanolamine or 3-aminopropan-1-ol in accordance with earlier patent applications EP 88118090.5 and EP 90107481.5. Tetramethylene bisoxazoline (a 15) was obtained in accordance with DOS 2 158 615; m-phenylene bisoxazoline was commercially obtainable (Showa Denko, Tokyo).

Table 1 contains further particulars of the individual compounds. Except for a3, the compounds are bisiminoethers (a3 is a triiminoether) which are all unsubstituted (formula I, R₁ -R₆ =H). Except for a7 (Z=CH₂ in formula I), they are polyoxazolines (Z=direct bond).

Component b

Both commercially available lactones (b16-b19) and monoiminoethers corresponding to formula II (R₁ -R₆ =H) were used as component b). Where the monoiminoethers were not commercially available (b10), they were prepared from carboxylic acids or esters thereof and ethanolamine or 3-aminopropan-1-ol in accordance with earlier patent applications EP 88118090.5 and EP 90107481.5 Further particulars of the individual compounds can be found in Table 2.

Component c

The following compounds were used as catalysts in the tests described herein:

c1 trifluoromethanesulfonic acid methyl ester

c2 p-toluenesulfonic acid methyl ester

c3 toluenesulfonic acid methyl ester (o-/p-mixture, technical, BASF)

c4 BF₃ etherate

                                      TABLE 1                                      __________________________________________________________________________     Polyimonoethers prepared from                                                  No.                                                                               Equivalent weight                                                                       Monoiminoether based on                                                                     Z  Polyisocyanate                                     __________________________________________________________________________     a1 448      Ricinoleic acid                                                                             -- MDI (4,4'-diphenylmethane                                                      diisocyanate)                                      a2 434      Ricinoleic acid                                                                             -- Isophorone diisocyanate                            a3 482      Ricinoleic acid                                                                             -- Desmodur ®                                                                 (N,N',N"-tris-{ω-isocyanato-                                             hexyl}-biuret)                                     a4 412      12-Hydroxystearic acid                                                                      -- TDI (2,4-toluylenediisocyanate)                    a5 282      6-Hydroxycaproic acid                                                                       -- MDI                                                a6 536      Epoxidized erucic ring-                                                                     -- MDI                                                            opened with methanol                                               a7 462      Ricinoleic acid                                                                             CH.sub.2                                                                          MDI                                                a8 407      Ricinoleic acid                                                                             -- 1,6-Hexamethylenediisocyanate                      a9 454      Ricinoleic acid                                                                             -- Desmodur ® W (4,4'-dicyclohexyl                                            methane diisocyanate)                              a10                                                                               268      6-Hydroxycaproic                                                                            -- Isophorone diisocyanate                                        (caprolactone)                                                     a11                                                                               445      Ricinoleic acid                                                                             -- Tetramethyl xylene diisocyan-                                                  ate (TMXDI ®)                                  a12                                                                               436      12-Hydroxystearic acid                                                                      -- Isophorone diisocyanate                            a13                                                                               456      12-Hydroxystearic                                                                           -- Desmodur ® W                                   a14                                                                               279      6-Hydroxycaproic acid                                                                       -- TMXDI ®                                        a15                                                                                98      Tetramethyl bisoxazoline                                           a16                                                                               118      m-Phenylene bisoxazoline                                           __________________________________________________________________________

                  TABLE 2                                                          ______________________________________                                              Equivalent                                                                               Carboxylic acid base of                                                                              Formula II                                No.  weight    the monoiminoether                                                                              Z    R                                         ______________________________________                                         b1   309       Stearic acid     --   C.sub.17 H.sub.35                         b2   309       Isosteary acid   --   C.sub.17 H.sub.35                         b3   300       Soybean oil fatty acid*                                                                         --   Mixture                                   b4   306       Conjuene fatty acid**                                                                           --   Mixture                                   b5   323       Ricinoleic acid  --   C.sub.17 H.sub.32 OH                      b6   225       Lauric acid      --   C.sub.11 H.sub.23                         b7   197       Capric acid      --   C.sub.9 H.sub.19                          b8   169       Caprylic acid    --   C.sub.7 H.sub.15                          b9   151       Head-fractionated fatty                                                                         --   Mixture                                                  acid (C.sub.6-12)***                                            b10   99       Propionic acid   --   C.sub.2 H.sub.5                           b11  147       Benzoic acid     --   C.sub.6 H.sub.5                           b12  314       Soybean oil fatty acid*                                                                         CH.sub.2                                                                            Mixture                                   b13  239       Lauric acid      CH.sub.2                                                                            C.sub.11 H.sub.23                         b14  161       Benzoic acid     CH.sub.2                                                                            C.sub.6 H.sub.5                           b15  183       2-Ethyl hexanoic acid                                                                           CH.sub.2                                                                            C.sub.7 H.sub.15                          b16  114       ε-caprolactone                                          b17   86       γ-butyrolactone                                           b18  100       γ-valerolactone                                           b19  100       δ-valerolactone                                           ______________________________________                                          *Fatty acid mixture of soybean oil (average C chain length of the              carboxylic acid: C.sub.18)                                                     **Edenor ® UKD 6010 (Henkel): fatty acid mixture containing conjugate      double bonds obtained by alkali isomerization (average C chain length:         C18)                                                                           ***Edenor ® V 85 KR (Henkel)                                         

Component d

In individual tests, the mixtures to be polymerized contain additives in the form of thickeners and/or binders:

d1 Polyester (Grilesta® P 7205, EMS Chemie)

d2 Polyester (Grilesta® V 73-9, EMS Chemie)

d3 Rilanit® HT (modified, hydrogenated fatty acid, Henkel)

d4-d12 Copolymers of monooxazolines corresponding to formula II prepared by cationic polymerization in accordance with the particulars of Example A of PCT/EP90/00019. For particulars, see Table 3. The molecular weights shown are weight average molecular weights determined by gel chromatography against polystyrene as standard.

                  TABLE 3                                                          ______________________________________                                         Polyoxazolines as additives                                                          Starting monomer:                                                                               Molar ratio                                                                              Molecular                                     No.   Oxazolines based on                                                                             in polymer                                                                               weight/10.sup.3                               ______________________________________                                         d4    (Soybean oil fatty                                                                              2:1:5      20**                                               acid/ricinoleic                                                                acid)/propionic acid                                                     d5    Lauric acid/propionic                                                                           1:10       11**                                               acid                                                                     d6    Lauric acid/propionic                                                                           1:10      11*                                                 acid                                                                     d7    Lauric acid/propionic                                                                           1:5       12*                                                 acid                                                                     d8    Stearic acid/benzoic                                                                            3:2       25*                                                 acid                                                                     d9    Stearic acid/propionic                                                                          1:10       12**                                               acid                                                                     d10   Soybean oil fatty                                                                               3:2       24*                                                 acid/benzoic acid                                                        d11   Capric acid/propionic                                                                           1:10       11**                                               acid                                                                     d12   Soybean oil fatty                                                                               3:2       22*                                                 acid/propionic acid                                                      ______________________________________                                          *Prepared in accordance with PCT/EP90/00019, method IV                         **Prepared in accordance with PCT/EP90/00019, method II                        (in either case with 1 mol% methyl tosylate, based on oxazoline)         

PROCESS EXAMPLES

Table 4 shows the composition of the mixtures used for coating and sets out the polymerization conditions. In the composition of the mixtures, the concentration of c is expressed in equivalent-%, based on a+b, while the concentration of d is expressed in % by weight, based on b. A recirculating air drying cabinet was used for curing.

TEST RESULTS

The coatings of Examples 1 to 78 were tested for their mechanical properties and for their adhesive strength on steel plates, aluminium plates and, in some cases, on glass. In every case, the layer thickness was 30 to 35 μm. Pendulum hardness was tested in accordance with DIN 53 157, impact indentation (reverse) in accordance with US standard ASTM-D 2795-69 and crosshatch adhesive strength in accordance with H. J. Peters (in Zeidler-Bleisch, Laboratoriumsbuch fur die Lack- und Anstrichmittelindustrie, pages 309-310, W. Knopp Verlag, Dusseldorf 1967), all the tests being carried out at room temperature. The results are shown in Tables 5 (iron plates) and 6 (aluminium plates and glass). Relatively high pendulum hardness and impact indentation figures respectively correspond to greater hardness and better flexibility of the coating. Crosshatch adhesion is visually evaluated on a scale of 0 (best adhesion) to 4 (poor adhesion). The excellent adhesion, even of particularly hard films, is particularly worth noting.

                                      TABLE 4                                      __________________________________________________________________________     Process Conditions                                                             Composition of the mixture                                                                                Component c                                                                            Component d                                            Component a:b      Concen- Concen-                                                                             Polymerization                      Component  b         (equivalent                                                                             tration tration                                                                             conditions                          Example                                                                             a     (molar ratio)                                                                            ratio)                                                                               Type                                                                              equ.-%                                                                              Type                                                                              % by wt.                                                                            t/min.                                                                             T/°C.                    __________________________________________________________________________      1   a1    b6        3:7   c1 2    d5 30   25  160                              2   a1    b8        3:7   c1 1    d5 30   15  160                              3   a1     b11      3:7   c2 1    d6 30   15  160                              4   a1    b6/b11 (1:1)                                                                             3:7   c2 1    d5 30   25  160                              5   a5    b6        3:7   c1 1    -- --   30  160                              6   a1    b6        3:7   c2 1    d3  3   30  160                              7   a1    b6        3:7   c2 1    d7 30   30  160                              8   a1    b6/b11 (1:1)                                                                             3:7   c3 1    d5/d6                                                                             15 + 15                                                                             25  160                              9   a1    b6        3:7   c2 1    d2 10   25  160                             10   a1    b6        3:7   c2 1    d1 10   25  160                             11   a1    b9        3:7   c1 1    -- --   30  140                             12   a1    b8        3:7   c1 1    d7 30   15  160                             13   a1    b8        3:7   c3 1    d9 30   30  140                             14   a1    b8        3:7   c1 2     d12                                                                              30   30  140                             15   a1    b8        3:7   c3 1    d8 30   20  160                             16   a6    b8        3:7   c2 1    -- --   20  160                             17   a1    b9/b2 (7:1)                                                                              3:7   c1 1    d6 30   20  160                             18    a15  b1        1:9   c2 1    -- --   30  160                             19   a1    b8        4:6   c1 1    d5 30   30  140                             20   a1    b11/b6 (1:1)                                                                             3:7   c1 1    d5/d6                                                                             15 + 15                                                                             20  160                             21   a1     b11      2:8   c3 1    d6 --   15  160                             22   a1     b11      3:7   c3 1     d11                                                                              30   45  120                             23   a1     b16      3:7   c2 1    -- --   30  160                             24   a1     b11      3:7   c1 1    d9 30   30  140                             25   a4    b7        3:7   c2 1    -- --   30  160                             26   a1     b11      3:7   c3 1     d12                                                                              30   30  160                             27   a1    b6        3:7   c1 1     d10                                                                              10   30  160                             28   a6    b6        3:7   c2 1    -- --   30  160                             29   a1     b11      3:7   c1 1    d4 10   30  140                             30   a1     b17      3:7   c1 1    -- --   30  160                             31   a1    b8/b16 (4:3)                                                                             3:7   c2 1    -- --   20  160                             32   a1    b8        3:7   c2 1    -- --   30  140                             33   a3    b7        3:7   c2 1    -- --   30  160                             34   a1     b10      1:9   c3 1    -- --   20  160                             35   a1    b8        2:8   c1 1    d5 30   30  140                             36   a7    b7/b4 (7:1)                                                                              2:8   c2 1    -- --   20  160                             37   a1     b11      4:6   c1 1    d6 30   45  120                             38    a2*  b7        3:7   c2 1    -- --   15  160                             39    a8*   b16      3:7   c2 1    -- --   30  160                             40   a1    b7/b12 (9:1)                                                                             3:7   c1 2    -- --   30  160                             41    a2*  b6/b8 (1:1)                                                                              4:6   c2 1    -- --   30  160                             42   a4    b13/b17 (2:1)                                                                            3:7   c3 1    -- --   30  160                             43   a1     b13      3:7   c2 1    -- --   30  160                             44   a1    b6/b16 (4:3)                                                                             3:7   c1 1    -- --   30  160                             45   a1    --        1:0   c1 1    -- --   30  160                             46   a1    b6/b14 (9:1)                                                                             4:6   c2 2    -- --   30  160                             47   a4    b11/b15 (9:1)                                                                            3:7   c2 2    -- --   30  160                             48   a1     b11      3:7   c1 1    -- --   30  140                             49   a1     b19      3:7   c2 1    -- --   25  160                             50   a1    b7/b13/b16 (1:1:1)                                                                       3:7   c2 1    -- --   30  160                             51   a1     b18      3:7   c3 1    -- --   30  160                             52   a4    --        1:0   c1 1    -- --   30  160                             53   a1    b6        8:2   c3 1    -- --   25  160                             54   a1    b6        9:1   c3 1    -- --   25  160                             55   a4    b7/b4 (9:1)                                                                              4:6   c3 1    -- --   30  160                             56   a1    b9/b1 (5:1)                                                                              3:7   c1 1    -- --   25  160                             57   a6    --        1:0   c2 1    -- --   30  160                             58   a1    b11/b3 (4:1)                                                                             3:7   c3 1    -- --   25  160                             59   a1     b11      9:1   c2 1    -- --   30  140                             60   a2    b6/b5 (9:1)                                                                              3:7   c1 1    -- --   30  160                             61   a1/a4 (1:1)                                                                           b11      3:7   c3 1    -- --   20  140                             62   a1    b6        3:7   c1 1    -- --   30  160                             63    a2*  b6        3:7   c3 2    -- --   25  160                             64   a7    b6        3:7   c1 1    -- --   30  160                             65   a9    --        1:0   c1 1    -- --   30  160                             66   a5     b11      3:7   c3 2    -- --   45  120                             67   a6     b11      3:7   c2 1    -- --   30  140                             68    a15  b6        3:7   c1 1    -- --   30  160                             69   a3    b6        3:7   c1 1    -- --   30  160                             70   a4     b11      3:7   c3 1    -- --   10  180                             71    a16  b7        3:7   c2 1    -- --   30  160                             72   a2    b7        3:7   c4 1    -- --   30  160                             73    a13  --        1:0   c3 1    -- --   30  160                             74    a12  --        1:0   c3 1    -- --   30  160                             75    a10  b7        3:7   c3 1    -- --   30  160                             76    a16   b11      2:8   c2 1    -- --   30  160                             77    a14  b7        3:7   c4 1    -- --   30  160                             78    a11  b7        3:7   c3 1    -- --   30  160                             __________________________________________________________________________      *Containing about 5% diisocyanate from production                        

                  TABLE 5                                                          ______________________________________                                         Coatings on steel plates                                                               Pendulum                                                                       hardness   Impact indentation                                                                            Crosshatch                                   Example s          inch × pound                                                                            adhesion                                     ______________________________________                                          1      183        >80            0                                             2      198        >80            0                                             3      200        >80            0                                             4      165        >80            0                                             5      200         10            4                                             6      130        >80            0                                             7      155        >80            0                                             8      179        >80            0                                             9      113        >80            0                                            10      150        >80            0                                            11      170        >80            0                                            12      186        >80            0                                            13      196         60            0                                            14      153        >80            0                                            15      175         60            0                                            16      167        >80            0                                            17      150        >80            0                                            18      154         20            4                                            19      192        >80            0                                            20      179        >80            0                                            21      186        >80            0                                            22      193        >80            0                                            23      188        >80            0                                            24      200         60            0                                            25      188        >80            0                                            26      167        >80            0                                            27      120        >80            0                                            28      120        >80            0                                            29      155        >80            0                                            30      183         40            0                                            31      193        >80            0                                            32      185        >80            0                                            33       93        >80            0                                            34      136        >80            0                                            35      195        >80            0                                            36       22        >80            0                                            37      193        >80            0                                            38      150        >80            0                                            39      172        >80            0                                            40      169        >80            0                                            41      110        >80            0                                            42      150        >80            0                                            43      168        >80            0                                            44      175        >80            0                                            45      168        >80            0                                            46      140        >80            0                                            47      155        >80            0                                            48      174        >80            0                                            49      176        >80            0                                            50      173        >80            0                                            51      183        >80            0                                            52       79        >80            1                                            53      187        >80            0                                            54      183        >80            0                                            55      141        >80            0                                            56       97        >80            0                                            57      140         20            0                                            58       40        >80            0                                            59      179        >80            0                                            60       21        >80            0                                            61      195        >80            0                                            71      182        <20            0                                            72       84        >80            0                                            73      134        >80            0                                            74      109        >80            0                                            75      204        >80            0                                            76      221        <20            1                                            77      218         20            0                                            78       85        >80            0                                            ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         Coatings on aluminium and glass                                                                      Pendulum  Crosshatch                                     Example                                                                               Substrate      hardness/s                                                                               adhesion                                       ______________________________________                                          5     Aluminium plate                                                                               154       1                                              22     Aluminium plate                                                                               169       0                                              28     Aluminium plate                                                                               168       0                                              45     Aluminium plate                                                                               172       0                                              63     Aluminium plate                                                                               185       0                                              64     Aluminium plate                                                                               188       0                                              65     Aluminium plate                                                                               137       0                                              66     Aluminium plate                                                                               200       3                                              67     Aluminium plate                                                                               162       0                                              68     Aluminium plate                                                                               172       0                                              69     Aluminium plate                                                                               126       0                                              70     Aluminium plate                                                                               175       0                                              22     Glass plate    182       0                                              62     Glass plate     99       0                                              ______________________________________                                     

What is claimed is:
 1. A process for coating a solid surface, in which a mixture ofa) a cyclic polyiminoether having at least two Δ² -oxazoline structures therein, b) optionally at least one compound selected from the group consisting of cyclic monoiminoethers having a Δ² -oxazoline structure, cyclic monoiminoethers having a Δ² -5,6-dihydro-4H-1,3-oxazine structure, and lactones containing 4, 5, 6 or 7 ring members, c) a cationic polymerization catalyst and d) optionally, auxiliaries and additives for coatings is applied to the surface and is polymerized on the surface by being heated; and wherein when component b) is present in the mixture the equivalent ratio of components a) and b) is from about 95:5 to about 5:95.
 2. A process as claimed in claim 1, in which components a and b are both present.
 3. A process as claimed in claim 2, in which component a is a bisiminoether.
 4. A process as claimed in claim 2, in which component a is an iminoether obtainable from reacting a polyisocyanate and a hydroxyl-functional cyclic monoiminoether.
 5. A process as claimed in claim 2, in which component b contains an oxazine or oxazoline that is substituted in the 2-position with a phenyl group or an alkyl group that has from 7 to 17 carbon atoms.
 6. A process as claimed in claim 2, in which an ester of trifluoromethanesulfonic acid or of a toluene sulfonic acid is used as the catalyst (c).
 7. A process as claimed in claim 2, in which at least one substance selected from the group consisting of pigments, thickeners and light stabilizers is present as component d.
 8. A process as claimed in claim 1, in which components a and b are used in an equivalent ratio of from 80:20 to 20:80.
 9. A process as claimed in claim 8, in which component a is a bisiminoether.
 10. A process as claimed in claim 8, in which component a is an iminoether obtainable from reacting a polyisocyanate and a hydroxyl-functional cyclic monoiminoether.
 11. A process as claimed in claim 8, in which component b contains an oxazine or oxazoline that is substituted in the 2-position with a phenyl group or an alkyl group that has from 7 to 17 carbon atoms.
 12. A process as claimed in claim 8, in which an ester of trifluoromethanesulfonic acid or of a toluene sulfonic acid is used as the catalyst (c).
 13. A process as claimed in claim 8, in which at least one substance selected from the group consisting of pigments, thickeners and light stabilizers is present as component d.
 14. A process as claimed in claim 1, in which component a is a bisiminoether.
 15. A process as claimed in claim 1, in which component a is an iminoether obtainable from reacting a polyisocyanate and a hydroxyl-functional cyclic monoiminoether.
 16. A process as claimed in claim 1, in which component b contains an oxazine or oxazoline that is substituted in the 2-position with a phenyl group or an alkyl group that has from 7 to 17 carbon atoms.
 17. A process as claimed in claim 1, in which an ester of trifluoromethanesulfonic acid or of a toluene sulfonic acid is used as the catalyst (c).
 18. A process as claimed in claim 1, in which at least one substance selected from the group consisting of pigments, thickeners and light stabilizers is present as component d. 